Chapter 1.2 (Processor performance) Flashcards
What factors affect processor performance?
- Clock speed
- The number of cores
- The amount and type of cache
What is clock speed measured in?
Hertz/ Giga hertz
What is 1 Hertz equivalent to?
One clock cycle per second
Why does clock speed affect the speed of the CPU?
The system clock generates a series of signals, each operation starts as the clock changes from 0 to 1.
The CPU can’t perform instructions faster than the clock speed.
So the higher the clock speed the faster the CPU performance.
How do traditional computers (Von Neumann architecture) process data?
Instructions are fetched and executed one at a time in a serial manner
What is a dual-core processor?
A processor with 2 processors linked together
Why does a dual core processor not always performs twice as fast as a single core processor?
Not all software are optimised to take full advantage of both processors, so the work may not be split equally between the two
What is cache?
Cache is a small amount of expensive, very fast memory inside the CPU
What is stored in the cache?
When an instruction is fetched from main memory it is copied into the cache, so if it is needed again soon after, it can be fetched from cache quicker than main memory
What are the different levels of cache?
LVL 1 - Small capacity, very fast
LVL 2 - Medium capacity, medium speed
LVL 3 - Largest capacity, slowest speed
Why is pipelining used?
Pipelining is a technique used by some processors to improve the performance, due to it’s ability to speed up the fetch-decode-execute cycle
What is pipelining?
Whilst the Fetch-decode-execute cycle is being carried out, the next instruction can be fetched and held in a buffer ready to be carried out
What is a GPU?
A graphical processor unit is a co-processor on a graphics card that perform simple instructions on a large data set
What are GPU’s used for?
Data mining (Bitcoin mining)
What is a co-processor?
A processor invented to increase speed of the computer and execute tasks concurrently
What is parallel processing?
Parallel computing is where we run multiple processes at one time
How can we use parallel processing?
- Multiple cores on the CPU
* Switching between instructions
How does parallel processing work?
Each core on the CPU can perform a fetch, decode, execute cycle independent of other cores.
Therefore if we have 2 cores, 2 processes can run at one time
How do you use multi-cores for parallel processing?
- Have software that takes advantage of multiple cores
* Have an operating system capable of using multiple cores.
